Clamp with pipe branch

ABSTRACT

A clamp for forming a seal on a pipeline section, the clamp comprising a pair of complementary clamp members to be clamped together, each clamp member having an inner surface with a pair of axially spaced, circumferentially extending circumferential seals, and one clamp member having a pair of circumferentially spaced longitudinal seals which extend axially to bridge the gaps between the opposed circumferential ends of the pair of circumferential seals to define four junction zones where the circumferential seals and the longitudinal seals abut, and retention means at each junction zone to connect the circumferential and longitudinal seals together in the retention zones, and at the same time connect the seals to the clamp member at the junction zones. The clamp includes corner seals to provide backup sealing from the junction zones. The clamp includes heat protection grooves to protect certain of the clamp seals. The clamp may include a pipe branch to provide a hot tapping facility. Embodiments of the clamp have an optimized body design to provide for weight minimization.

The present application is a divisional of U.S. Ser. No. 364,628, filedJune 8, 1989, now U.S. Pat. No. 5,004,275 which is a divisional of U.S.Ser. No. 237,308, filed Aug. 26, 1988, now U.S. Pat. No. 4,895,397,which is a continuation of U.S. Ser. No. 840,329, filed Mar. 14, 1986,now U.S. Pat. No. 4,790,058.

This invention relates to a clamp. More particularly this inventionrelates to a clamp for use in forming a seal on a pipeline section. Theclamps of this invention are particularly adapted to serve as repairclamps for use in repairing leaks or weakened zones in high pressurepipeline sections. They may also be used to reinforce pipeline sectionsin weakened zones or in zones which are vulnerable to damage or toadditional stress.

Known high pressure pipeline repair clamps are generally expensivebecause of the high cost of manufacture, are frequently not as reliableas required by the function which they serve, and are often difficultand clumsy to install.

Clamps which are intended to be mounted onto existing pipeline sections,such as, for example, repair clamps, branch clamps, tapping clamps, andthe like, comprise separate components which can be fitted together tocomplete the clamp. Such clamps are therefore usually split clamps whichare split into circumferential sections to enable them to be mountedonto a pipeline sections. The seals of such clamps thus cannot bemonolithically constructed to surround the pipe circumference.Difficulties are therefore often encountered in locating seals in theclamp members or sections of such pipeline clamps. This is in contrastto full annular seals which can often be retained in seal grooves simplyby interference. The seals in the components of such pipeline clamps,experience significant loads as the clamp is installed on a pipe sectiondue to the interference which is necessarily designed in the seals. Themost prominent forces exerted on the seals tend to occur at the splitseams between the clamp members where friction from squeezing andsliding the seals into position tends to slide the seals out of positionduring installation.

Attempts have been made to retain the seals of such clamps, particularlyof repair clamps, in position by using retainer rings which are mountedon the clamp members and compress portions of the seals onto the bodiesof the clamp members. These retainer rings can be effective at retainingthe seals in position. However, the retainer rings can sometimes damagethe seals. Sometimes the retainer rings can be so effective at sealretention that the seals do not have sufficient freedom of movementnecessary to fill imperfections in a pipeline surface or to engagesealingly with adjacent or abutting seals. Other attempts have been madeto provide dovetail seal grooves in the repair clamp member to locatecorrespondingly shaped seals. Dove tail seal grooves require specialmachining during manufacture and are more costly to manufacture due tothe additional detail of cutting the reverse angle groove walls.

Where seals are located securely on clamp members of repair clamps, alarge effort is often necessary to replace the seals. Many users ofpipeline repair clamps use them temporarily. When conditions permit, thepipeline is permanently repaired and the repair clamp is recovered forfuture use. This requires replacement of the used seals with new seals.It is desirable, therefore, that repair clamps have seals which arereadily replaceable when desired. Where the seals are difficult toreplace, users often discard the entire clamp rather than incur the costcharged for refurbishing such repair clamps.

It is an object of one aspect of this invention, to provide a clamp,particularly a pipeline repair clamp for repairing high pressurepipelines, which can overcome or at least reduce the disadvantages ofthe prior repair clamps discussed.

In accordance with one aspect of this invention, there is provided aclamp for forming a seal on a pipeline section, the clamp comprising atleast two complementary clamp members to be clamped together on apipeline section to complete the clamp; each clamp member having aninner surface with a pair of axially spaced, circumferentially extendingcircumferential seals; at least one clamp member having at least onelongitudinal seal which extends axially to bridge the gap between a pairof circumferential seals and define two junction zones where the twocircumferential seals and the longitudinal seal abut; and retentionmeans at each junction zone, each retention means penetrating at leastone of the seals to connect the seals together in the junction zone.

The clamp is particularly suitable as a high pressure repair clamp forrepairing leaks or defects in high pressure pipeline sections.

Each retention means may preferably be connected to a clamp member toconnect the seals with which it is engaged, to such clamp member.

In a preferred application of the invention, each retention meansextends through one of the seals and penetrates the adjacent seal tothereby connect the two seals together at that junction zone.

The retention means may be in the form of various types of mechanicaldevices which can positively connect abutting seals together to form aseal, for example, nails, pins, brads or shafts. In a preferredembodiment of the invention the retention means comprises a self-tappingscrew which extends through one seal and is screwed into the adjacentseal. In this embodiment of the invention, the clamp member preferablyhas bores through which the screws extend to thereby secure the sealswith which they are engaged, in position on the clamp member.

The seals may be located in appropriately positioned seal grooves in theclamp members. The clamp may include one or a plurality of additionalretention means which connect the seals to their respective clampmembers in one or a plurality of connection zones to thereby retain theseals in position.

In an embodiment of the invention, the clamp members may have heatprotection grooves in their inner surfaces between selected peripheraledges of the clamp members and selected seals, to protect the seals fromheat flow towards the seals during welding of such peripheral edgesduring use.

The clamps of this invention may have corner seals positioned to abutthe junction zones and provide secondary sealing for the junction zonesduring use.

The clamp may have one clamp member with a pipe branch extendingtherefrom. In this embodiment of the invention, the clamp member mayhave an annular gasket to seal a peripheral zone proximate the pipebranch to a pipeline section when the clamp is sealingly engaged withsuch a pipeline section. In this aspect of the invention, the clamp mayalso have one clamp member with a test port.

Users of high pressure pipeline repair clamps sometimes prefer to weldthe clamps onto a pipeline section subsequent to repair of the leak withthe clamp. This makes the clamp a permanent fixture of the pipeline andeliminates the dependence of sealing integrity on the elastometric sealsof the clamp. The usual procedure is that the repair clamp is installedto seal the leak. Then the area is cleared of any combustible productswhich may have leaked from the pipeline. The pipeline is brought up tosteady flow conditions to dissipate welding heat and thereafter theseams and openings of the clamp are welded.

Seal welding of a repair clamp does present certain dangers. If the heatproduced by welding conducts to the seals in sufficient quantity toexceed the temperature capabilities of the seal material, the sealmaterial may fail prior to completion of the seal welding procedure. Ifthe pipeline product is combustible, this can create a hazard.

Attempts have been made to combat this problem by adding excess steel tothe axial ends of the clamp to absorb the welding heat when those axialends are welded to the pipeline section, and thus prevent excessivequantities of heat being conducted to the seals. Usually the amount ofadded metal is approximately three inches on each axial end. This addedmetal is heavy, adds to the cost of the product, and is wasteful whereseal welding is not employed.

It is accordingly an objective of a further aspect of this invention, toprovide means for overcoming or reducing the problem presented by heatconduction to seals during seal welding of repair clamps and otherclamps.

In accordance with this aspect of the invention, there is provided aclamp for a tubular member, the clamp having an inner wall surface,having a sealing groove in the inner wall surface to house seal means,the sealing groove being spaced from a peripheral zone of the clamp, andthe clamp having a heat protection groove, the heat protection groovebeing provided in the inner wall surface between the peripheral zone ofthe clamp and the sealing groove to interrupt heat flow from theperipheral zone to the sealing groove to thereby partially protect sealmeans when housed in the sealing groove during use, against heat flowfrom the peripheral zone during welding thereof.

The invention further extends to a clamp for pipeline repair, the clampcomprising a plurality of clamp members to be clamped to each otherabout a pipeline to be repaired to complete the clamp, each clamp memberhaving a sealing zone for receiving seal means, and each clamp memberhaving a heat protection groove between the sealing zone and aperipheral zone of the clamp member to interrupt heat flow from theperipheral zone to the sealing zone during welding of the peripheralzone and thereby provide protection of seal means when positioned in thesealing zone. Moreover, heat protection grooves may be extended axiallyto protect the circumferential seals and the longitudinal seals, or aportion of the longitudinal.

The heat protection grooves may have depths generally corresponding tothe depths of the sealing grooves. They may, however, have greater orlesser depths depending upon the configuration of the clamp members andthe proposed welding conditions. If desired, insulation material may behoused or fixed in the heat protection grooves to provide further heatinsulation.

Since repair clamps require both circumferentially extending and axiallyextending seals, and since repair clamps comprise two or more clampmembers which are clamped together to complete the repair clamp on apipeline section, a plurality of seal junction zones occur whereseparate seals abut. These are the most sensitive areas for sealingreliability in leak repair clamps.

These junction zones are generally areas where seal-to-seal contactoccurs. In other areas of the clamp in accordance with this invention,the seals can generally be arranged so that seal-to-metal contact isutilized. Where the seals are in direct contact with metal, sealperformance is very predictable and reliable. However, extensiveseal-to-seal contact can tend to be unreliable.

It is a further object of this invention to provide means for improvingthe reliability of sealing in such junction zones.

In accordance with this further aspect of the invention, there isprovided a clamp for forming a seal in a pipeline section, the clampcomprising at least two complementary clamp members to be clampedtogether on a pipeline section to complete the clamp, each clamp memberhaving an inner surface with a pair of axially spaced, circumferentiallyextending circumferential seals, at least one clamp member having atleast one longitudinal seal which extends axially to bridge the gapbetween the ends of a pair of circumferential seals and define twocorner junction zones, and at least one clamp member having at least onecorner seal positioned to abut a junction zone during use and provideback-up sealing for the junction zone when the clamp is completed duringuse.

The clamp preferably has a corner seal positioned at each cornerjunction zone to embrace the outwardly directed edges of the seals inthe corner junction zones.

The corner seals are preferably located in corner recesses provided inthe clamping members to allow an appropriate degree of compression ofthe corner seals during use.

Particularly, for example, when using conventional high pressure sealingmaterials, the corner recesses may be such in relation to the designedfor compression of the seals, that the corner seals can be compressed by30 or 40 percent during completion of the repair clamp.

The corner seals are preferably employed for very high pressureapplications. They will tend to be less important or unnecessary inmedium or high pressure applications.

The clamp preferably includes retention means to retain the corner sealsin position on the clamp members.

In an embodiment of the invention, the retention means may comprise theretention means used for retaining the circumferential and longitudinalseals in position.

Pipeline repair or leak repair clamps are often used in hot-tapping andline-stopping applications. Such variations are often used in linemaintenance and construction projects as well as in those cases wherepipeline leaks are to be repaired or pipe sections are to be replaced.

Prior art clamps of this type are generally simply a leak repair clampwith a pipe branch attached to extend from the clamp.

These prior art branch clamps have certain disadvantages and createcertain concerns.

First there are concerns about the reliability of the seals and the highcost of failure in the event of leakage. Often no leak exists (at thetap location) prior to tapping into the pipeline. A fitting maytherefore be successfully installed with no indication of a leak sincethe pipeline has not yet been tapped. However, after the line is tapped,pipeline pressure is applied to the interior of the fitting. At thiscritical time a leak may be observed for the first time. Since a hole,which can be of a significant size, has by then been bored through thepipe, the fitting cannot practically be removed, and no convenientmethod exists to stop the leak. This, therefore, usually necessitatestaking the pipeline out of service in order to replace the leakingfitting.

A further concern is based on the fact that, after a tap is effected,the pipeline fluids are free to circulate in the annular space formedbetween the interior of the tapping fitting or branch fitting, and theoutside of the pipe. Pipeline fluids may be corrosive or damaging toseals. Pipelines usually have internal coatings applied to resist thedeleterious effects of the pipeline product. However, the exterior ofthe pipe does not usually have the same protection. It is often,therefore, considered undesirable to have free movement of the pipelineproduct on a region of the pipeline exterior.

It is accordingly a further objective of this invention, to provide aclamp which can serve as a branch clamp, and which can reduce orovercome some of the discussed advantages.

In accordance with this further aspect of the invention, there isprovided a clamp for clamping sealingly onto a pipeline section, theclamp comprising at least two clamp members to be clamped together on apipeline section to complete the clamp, each clamp member having sealzones for receiving seal means to provide a sealing engagement betweenthe clamp and a pipeline section during use, one clamp member having apipe branch extending therefrom for the clamp to serve as a tappingsaddle or branch clamp, and that clamp member having an annular gasketto be positioned within the clamp member about the inner periphery ofthe pipe branch for sealing engagement with a pipeline section duringuse.

The gasket preferably comprises a pliant gasket which can conformclosely with the pipeline surface during use, and can isolate the pipebranch zone from the remainder of the interior of the clamp.

In a preferred embodiment of the invention, the gasket comprises aperforated elastomer sheet which is relatively pliant to be tolerant ofpipe dimensions and pipe surface defects.

In the clamp of this aspect of the invention, at least one clamp membermay include a test port to provide access to the interior of the clampto a zone between the annular gasket and the seal means of the clampmembers during use.

The seals and annular gasket used in the clamps of this invention, maybe made of any conventional or suitable materials which can serve therequired purpose. There are a number of standard materials of differenttypes which are commercially available. Appropriate seals can bepurchased off the shelf, can be extruded to specification, or can bemolded to specification.

Various synthetic rubbers are, for example, available which are suitablefor seals in the clamps of this invention.

For line temperatures below about 300° F. buna nitrile synthetic rubbersare generally preferred. For temperatures at 300° F. or higher, fluoroelastomers, such as those for example available under the trademark"VITON" are currently preferred.

Silicon seals are also sometimes used.

The particular seal material depends on the chemical composition in thepipeline, the operating temperature, and the operating pressure. Fromthese parameters, persons of ordinary skill in art can readily selectappropriate seal materials from those commercially available, and canreadily design the dimensions and compression ratios from the ratingswhich are available for various applications.

Seal materials are graded by a standard, referred to as a durometerreading, which gives an indication of the stiffness of the rubber.

The preferred seal material for average conditions for a repair clamp ofthis invention, is a buna nitrile seal operating at a temperature ofless than 250° F. For an ANSI class 600 rating (that is 1,480 psi atambient temperatures) a durometer reading of 70 to 75 is preferred.

The materials from which the clamp members are made, are well-known topersons of ordinary skill in the art. They may be selected from thevarious steels which are listed in available piping and pressure vesselcodes.

Where welding will be employed for the clamp of this invention, thematerial of the clamp must be selected that neither the material of theclamp nor the material of the weld will be compromised during welding.

The clamp materials may for example comprise carbon steel casting ASTMA-216-grade WCA, WCB or WCC. Applicant's presently preferred grade isgrade WCC.

While the clamps of this invention can have various applications, theyare particularly suitable for and adapted for use in pipeline repair andhigh pressure pipeline repair or sealing operations.

A further concern is based on the fact that the clamps for use informing a seal on a pipeline section, particularly where the pipeline tobe clamped is of large diameter, are quite heavy and additionally, quitebulky. It has generally been thought that in order to combat the highpressures and temperatures associated with pipeline repair clamps, itwas necessary to add additional weight to the clamp. Clearly, however,such weight costs money. Material costs are significant to the cost ofthe product. Transportation charges are directly related to shippingweight. Additionally, installation is made more difficult by the highweight.

Accordingly, the present invention also provides clamps of reducedweight which are rated to withstand the same at higher operatingpressures. This weight reduction, while retaining or increasing theclamp performance, is due to a reduction in bending loads in the clampbody that result from internal pressure. Such reduction in bending loadsis achieved by adjusting the primary path of tensile loads in the clampbody and in the bolts.

The primary tensile loads associated with a pipe clamp having a pair ofcomplementary clamping members to be clamped together to form a clampbody, are defined radially around a tensile load centerline of the clampwall and laterally along a bolt force centerline defined by the boltpositioning on the bolting flanges. Therefore, by adjusting the relativepositioning of the two tensile load forces, that is, the bolting forcecenterline and the wall tensile load centerline, clamps may be designedwhich achieve a minimized weight yet which meet at least minimumacceptable criteria for clamp wall thickness, clamp body bending stressand bolt bending stresses.

The wall tensile load centerline, commonly referred to herein as a wallcenterline may generally be defined as being projected along a radialpath extending from a mid point between the inner and outer surfaces ofthe clamp walls, the radial path generally corresponding to thecurvature of the curved inner wall surface. In the completed clamp, thatis, a clamp in a closed or clamped position, the wall centerline maygenerally be envisioned as an annular tensile load defined radiallyaround a central point, the central point generally being defined as theaxial center of the clamp body bore, alternatively, the axial center ofthe pipe to be clamped.

The bolt force, or tensile load, centerline is generally defined by thebolt hole or bolt bore, more specifically, the axial center of the bolthole or bore.

It will be appreciated that adjustment of the bolt force centerline withrespect to the wall centerline may result in a clamp body cavity with anon-circular bore. Pipes are nevertheless sealing engaged by the presentclamps through the use of axially spaced sealing flanges which extendfrom the clamp walls and have radii roughly corresponding to the radiusof the pipe.

Embodiments of the invention are now described by way of example withreference to the accompanying drawings.

In the drawings:

FIG. 1 shows a three dimensional view of one preferred embodiment of arepair clamp for forming a seal on a pipeline section, with the clamp inits unassembled condition;

FIG. 2 shows a partly sectional, partly broken away, end view in theaxial direction of a preferred embodiment of the repair clamp of FIG. 1,in its completed or assembled condition on the pipeline section or asection of some hollow tubular member;

FIG. 3 shows a fragmentary, sectional view, to an enlarged scale, of theclamp of FIG. 2, along line III--III thereof;

FIG. 4 shows a fragmentary, sectional view, to an enlarged scale, of theclamp of FIG. 2 along the line IV--IV thereof;

FIG. 5 shows a fragmentary plan view of the clamp in accordance withthis invention having corner seal means;

FIG. 6 shows a sectional side elevation of the clamp member of FIG. 5,along line VI--VI of FIG. 5;

FIG. 7 shows a sectional end elevation, in the axial direction, of analternative embodiment of the clamp of FIGS. 1-6, which is in the formof a tapping saddle or branch clamp.

FIG. 8 shows an end view in the axial direction of a typical prior artclamp, with arrows indicating the off-set of clamp body tensile loads;

FIG. 9 shows a sectional view of a clamp having a zero off-set betweenthe wall centerline and the bolt force centerline;

FIG. 10 shows a sectional end view in the axial direction of a preferredembodiment of repair clamps produced in accordance with the presentinvention, demonstrating an optimized off-set and non-circular clampbore;

FIG. 11 is a graphic display of changes in the clamp weight achieved byvarying the force centerline off-set, and particularly demonstrates theexistence of a minimum clamp weight achieved at an optimum off-setvalue;

FIG. 12 illustrates a logic circuit or flow chart for data processinguseful in the minimization of clamp weight.

With reference to FIGS. 1-4 of the drawings, reference numeral 10 refersgenerally to one preferred embodiment of a clamp in accordance with thisinvention for forming a seal on a pipeline section.

The clamp 10 is in the form of a repair clamp for the repair of highpressure pipeline sections to stop leaks or repair defects.

The clamp 10 comprises two complementary clamp members 12.1 and 12.2which are designed to be clamped together on a pipeline section tocomplete the clamp 10.

Each of the clamp members 12 (that is 12.1 and 12.2) has inner flangesurfaces 14 which are generally semi-annular.

The clamp members 12 are generally semi-annular because two clampmembers 12 are used to complete the clamp 10. It would be appreciated,however, that more than two appropriately shaped clamp members 12 couldbe used to complete the clamp 10. A pair of clamp members 12 is howeverthe present preferred configuration.

Each of the flange surfaces 14 of the clamp members 12, has a pair ofaxially spaced circumferentially extending circumferential seal grooves16 wherein circumferential seals 18 are located. These circumferentialseals 18 of each clamp member 12 are thus axially spaced and extendcircumferentially. They are provided in the inner flange surfaces 14.

Only one of the clamp members, namely the clamp member 12.2, has a pairof circumferentially spaced, axially extending, longitudinal sealgrooves 20.

The longitudinal seal grooves 20 are provided at the circumferentiallyopposed ends of the circumferential seal grooves 16 and thus of theclamp member 12.2.

Each seal groove 20 has a longitudinal seal 22 positioned therein.

The longitudinal seals 22 abut the circumferential seals 18 to definefour junction zones 24.

The inner flange surfaces 14 of the clamp members 12 are defined alongthe inner peripheries of inwardly extending flanges 26 which are axiallyspaced from each other to define recesses 28 between the flanges 26.

Each clamp member 12 has a clamp flange or bolting flange 30.1 (for theclamp member 12.1) and 30.2 (for the clamp member 12.2) at thecircumferentially opposed ends. The flanges 30 are used for bolting theclamp members 12 together to complete the clamp 10.

Each flange 30 has a plurality of bolt holes or bores 32 for receivingbolts or studs to clamp the clamp members 12 together.

Each flange 30 has a seating face 34.

The seating faces 34 of the clamp member 12.2 have the longitudinal sealgrooves 20 provided therein. The longitudinal seals 22 thereforecooperate with he seating faces 34 of the clamp member 12.2 and with heseating faces 34 of the clamp member 12.1 when the clamp 10 is completedon a pipeline section.

Each clamp member 12 has a curved outer wall surface 36 and a curvedinner wall surface 38 between the flanges 26. Each flange 30 has a boltsurface 40.

During use the clamp members 12 are clamped together by means ofappropriate bolts. In the preferred embodiment illustrated in thedrawings, the bolts are in the form of socket head cap screws 42 havingsocket heads 44. Hexagonal nuts 46 are used with the screws 42.

Since the socket head cap screws 42 are tightened with a male driverkey, it is not necessary to provide excess spacing around the bolt head44. The bolts may thus be spaced more closely to each other, and moreclosely to the outer wall surfaces 36 of the clamp members 12. This canlead to a significant reduction in the size of the flanges 30 of theclamp 10.

The offset between the bolt or capscrew 42 center lines and the centerline of the clamp body, may be minimized for the same reason, leading toless bending loads on the clamp body.

Since the socket head 44 diameters are less than the width across theflat portions of the nuts 46, the flanges 30 are conveniently shaped sothat the nuts 46 cooperate with corners formed between the junctions ofthe bolt surfaces 40 and the outer wall surfaces 36 to prevent the nuts46 from rotating during installation. This therefore eliminates the needfor a back-up wrench during bolt torque procedures.

While socket head cap screws of any conventional materials may be used,the present preferred screws 42 are those produced under ANSI B18.3which specifies material according to ASTM A-574. The materialspecification specifies a minimum 0.2% offset yield strength of 153,000psi and a minimum ultimate tensile strength of 170,000 psi. A minimumelongation (before fracture) of 8% is also specified for the material.Because of the higher strength, the length of pipeline sectionencapsulated may be increased without using larger bolts or screws 42.Alternatively, the same length may be encapsulated or sealed usingsmaller bolts. This is important since an increase in bolt size alsoincreases the size and weight of the clamp 10.

The cumulative weight savings which can result from the use of sockethead cap screws of high strength, attributable to the weight of thescrews 42 and the reduced possible dimensions of the bolting flanges 30,and the concomitent lesser bending loads on the clamp body from anoptimized design in accordance with this invention, can provide a weightsaving of typically from about 15% to a saving which may be as high as40% in some cases.

The clamp member 12.2 includes retention means 48.1 which connect thelongitudinal seals 22 to the circumferential seals 18 in the fourjunction zones 24. At the same time, the retention means 48.1 serve tosecure the longitudinal seals 22 and the circumferential seals 18 inposition to the clamp member 12.2.

Each retention means 48.1 comprises a self tapping screw 48.1 whichextends through a bore 50 in the flange 26, which is screwed through thecircumferential seal 18, and into the longitudinal seal 22. (As can beseen particularly in FIG. 4.)

Each retention means, or self-tightening screw 48.1, thus positivelysecures the circumferential seal 18 to the longitudinal seal 22 in thejunction zone 24, while at the same time positively locating thejunction zones 24 in position on the clamp member 12.2.

The clamp members 12 include additional retention means 48.2 whichlikewise extend through bores 50 in the flanges 26, and penetrate thecircumferential seals 18 in connection zones to connect thecircumferential seals 18 to the clamp members 12 in those connectionzones.

The additional retention means 48.2 will be provided at spaced intervalsalong the length of the circumferential seals 18, with the spacingdepending upon the diameter of the clamp 10. Receiving bores may beprovided at appropriate intervals in the flange 26 to receive the freeends of the retention means 48.2 which pass through the circumferentialseals 18.

The embodiment of the invention as illustrated in FIGS. 1-4 of thedrawings, provides the advantage that the retention means 48 effectivelylocates the circumferential seals 18 in position in the seal grooves 16of the clamp members 12. In addition, the retention means 48.1 securethe ends of the circumferential seals 18 and longitudinal seals 22together in the critical junction zones 24 to improve the sealing effectin the zones, while simultaneously locating the ends of thecircumferential seals 18 and of the longitudinal seals 22 in position inthese junction zones.

The seal retention means 48 effectively supports the seals duringinstallation, and does not restrict the seals from filling imperfectionsin the pipe surfaces during use. Additionally, the seal retention meansallows easy replacement of the seals when required.

The use of the retention means 48 in accordance with the aspect of theinvention described with reference to the preferred embodiment of FIGS.1-4, provides several advantages. This aspect of the invention providessimplicity. Conventional self threading screws are used to penetrate theseals and provide a firm holding power on the seals. The retention means48.1 comprises a single self-tapping screw per corner junction 24, andserves the dual purpose of locating the seal in position while keepingthe number of screws to a minimum. Installation of the seals issimplified. The labor savings resulting from the ease of installation ofthe seals and the retention screws, and the ease of replacement, reducesthe cost of manufacture and can decrease delivery time.

Applicant was surprised that retention means in the form of self-tappingor threading screws could be used for the purpose disclosed. Applicantbelieved that such screws would weaken the seals and that the tendencyto leak at the penetration points would be great. Surprisingly, theelastomer materials of the seals create tight seals along the retentionmeans 48 and test have shown that leaks are unlikely in these regions.In addition, the retention means 48.1 create effective seals at thejunction zones of the circumferential and longitudinal seals therebyresisting leakage in the corner junction zones 24. In fact the retentionmeans 48.1 reinforce the seals in the leak sensitive corner or junctionzones 24 and do not appear to have any harmful effect on the sealingproperties of the seals.

Each clamp member 12 further has circumferentially extending heatprotection grooves 52 provided in the inner surfaces of the flanges 26.

The circumferentially extending heat protection grooves 52 are providedbetween the circumferential grooves 16 and the axial ends of the clampmembers 12. The heat protection grooves are clearly visible in FIGS. 3and 4 of the drawings.

The purpose and function of the heat protection grooves 52 isdemonstrated more particularly with reference to FIG. 3 of the drawings.

The repair clamps of this invention are often welded to a pipelinesection once they have been mounted in position. At the same time theclamp members 12 are welded together. The clamp 10 thus becomes apermanent part of the pipeline section to which it is welded. Thesealing reliability of the repair clamp it is thus no longer dependentupon the sealing effect of the elastomer seals 18 and 22.

In FIG. 3 a typical weld 54 is shown welding the axial end of the clampmember 12 to a high pressure pipeline section 56.

During the welding operation, heat is generated. If the quantity of heatwhich is conducted along the flange 26 towards the circumferential seal18, becomes excessive, the seal 18 can lose its sealing effect duringthe welding operation. During the welding operation, fluids are conveyedthrough the pipeline 56 to dessipate heat generated during welding.Deterioration of the seal 18 is undesirable and can thus be harmful ifit occurs during the welding operation. It can also, of course, bedangerous if combustible materials are be conveyed in the pipelinesection 56.

The heat protection groove 52 interrupts the heat flow path therebylimiting the quantity of heat conducted from the weld zone 54 to thecircumferential seal 18 during welding.

The heat protection groove 52 conveniently has a width of about 1/8",and a depth generally corresponding to the depth of the circumferentialseal grooves 16.

The heat protection groove 52 provides advantages over the prior artsystems of increasing the axial widths of the flanges 26 by about 3inches to absorb the heat generated and thus protect the seals. The heatprotection grooves 52 do not add to the weight of the clamp 10 andprovide a more effective barrier to the transfer of heat than additionalmaterial in the clamp members 12.

The clamp 10 includes a plurality of corner seals 58. The corner sealsare illustrated in detail in FIGS. 5 and 6 of the drawings. For the sakeof clarity, the corner seals 58 have been omitted from FIG. 1 and fromFIG. 4.

With particular reference to FIGS. 5 and 6 of the drawings, therefore,four corner seals are provided on the clamp member 12.2 at the fourcorner junction zones 24.

The corner seals 58 are positioned in the appropriate recesses 60 in thesealing face 34. The recesses 60 communicate with their adjacentcircumferential seal grooves 16 and longitudinal seal grooves 20.

Each corner seal 58 is shaped to be located in its recess 60, and toembrace the adjacent circumferential seals 18 and longitudinal seals 22where they join at the corner junction zones 24.

The corner seals 58 are positioned so that the retention means orself-tapping screws 48.1 also pass through the corner seals 58 beforepenetrating and passing through the circumferential seals 18, and thenpenetrating the longitudinal seals 22. The retention means 48.1 thusserve to additionally locate the corner seals 58 in position, and tosecure them to the seals 18 and 22.

The junction zones 24 are the most sensitive zones for sealingreliability in repair clamps. These are the areas where leaks are mostlikely to occur because the longitudinal seals abut the circumferentialseals in these areas. In addition, in these junction zones, seal-to-sealcontact occurs during use, as opposed to seal-to-metal contact. Theclamp members 12 are specifically designed to provide seal-to-metalcontact in most areas. That is why the longitudinal seals 22 areprovided on the clamp member 12.2 only, so that they can co-operate withthe sealing faces 34 of the clamp member 12.1.

The corner seals 58 do not eliminate the seal-to-seal contact, butcompletely surround the area in question with metal-to-seal contact. Thecorner seals 58 therefore provide a relatively reliable sealing geometryas a back up or secondary sealing system to the primary seal provided bythe seals 18 and 22.

The corner seals 58 may conveniently be installed as circular pads whichare located in the recesses 60 and are then cut so that they do notextend over the seal grooves 16 or 20 in the junction zones 24.

In practice, for average conditions, the longitudinal seals 22 andcircumferential seals 18 would project about 1/4" or so above thesurfaces of the clamp members. The recesses 60 are thereforeconveniently made so that, upon proper compression during use, thecorner seals will have compressed by about 30 to 40 percent of theiroriginal height.

With reference to FIG. 7 of the drawings, reference numeral 62 refersgenerally to an alternative embodiment of a clamp in accordance withthis invention for forming a seal on a pipeline section.

The clamp 62 corresponds substantially with the clamp 10 of FIGS. 1-6.Corresponding parts are therefore indicated by corresponding referencenumerals.

The clamp 62 is in the form of a tapping saddle or branch clamp whichmay be used to provide a tap into a pipeline section, or which may beused to provide such a tap when a repair is made.

The clamp member 12.1 of the clamp 62 has a pipe branch 64 extendingthereform.

The clamp 62 includes an annular gasket 66 which is positioned withinthe clamp member 12.1 proximate the inner periphery of the pipe branch64 to provide a sealing engagement with the pipeline section 56 duringuse as shown in FIG. 7.

The clamp 62 further includes a sealable test port 68 which is providedin the clamp member 12.1.

The annular gasket 66 is preferably made of a material which correspondswith that of the longitudinal and circumferential seals 22 and 18 asdiscussed in the specification. As such the gasket is pliable andtolerant to pipe dimensions and surface defects in the pipeline section.

The gasket is located in an annular gasket recess 70 along the innersurface of the clamp member 12.1.

Since the annular gasket 66 closely surrounds the tapping area once thetapped hole 72 has been formed in the pipeline section 56, access by thepipeline fluids to the exterior of the pipe section 56 will berestricted to the very small area around the tapped hole 72. Theexternal surface of the pipeline section 56 is therefore protected bythe annular gasket from any corrosive action of the pipeline fluids.

The clamp 62 provides a more important benefit in that it allows testingof the clamp 62 for sealing integrity prior to actual tapping of thepipeline section 56. By using the test port 68, hydrostatic pressure maybe applied between the gasket 66 and the conventional circumferentialand longitudinal seals of the clamp 62 to test the seals and verify thatthe seals are effective. This practically insures that no leakage willoccur when the pipeline section 56 is tapped. Without the annular gasket66 of the clamp 62, it is generally only possible to determine whetheror not the conventional seals are effective once the tapped hole 72 hasbeen formed and the fluid under pressure enters the interior of clamp62. If a leak is detected at that stage, after the tapped hole 72 hasbeen formed, it is a serious disadvantage.

The clamp 62 provides the further advantage that if a leak occurs in theclamp 62 sometime after installation, the test port 68 may be used toinject an appropriate sealant into the cavity defined by the outerperiphery of the gasket 66, and by the outer peripheries of thelongitudinal and circumferential seals 22 and 18. A leak may thereforebe repaired without taking the pipeline out of service. This isgenerally not possible if no such annular gasket 66 is included, becausethe sealant will then flow into the bore of the pipe and will not beeffective in sealing the leak.

Referring now to FIGS. 8-10, there is shown cross-sectional views ofvarious repair clamps. FIG. 8 shows the basic body shape of aconventional repair clamp 70. Note that the clamp body bore 72.8 of theclamp 70 is basically circular. The dash lines displayed thereinindicate the primary path of the wall tensile load centerline 74.8. Itshould be observed that a significant distance results between the boltforce centerline 42.8 and wall centerline 74.8 at the clamp seam 76.8defined by the seating faces 34.8. Arrows (78.8) illustrate the off-setdistance 70.8 between the wall centerline 74.8 and bolt centerline 42.8.

It will be appreciated that the product of the off-set distance 78.8 andthe tensile load along the bolt centerline 42.8 is the value of thebending moment induced in the shell of the clamp. Further, this momentis constant and continuous from one wide of the shell to the other.Therefore, where the off-set distance 78.8 is a large value, the bendingmoment is also a large value. Such large bending moments are undesirablein that these loadings must be resisted by the clamp body which leads toan increase in the body wall thickness or alternatively to the use ofexpensive stiffening ribs. Additionally, the clamp may not deflectsignificantly without endangering the loss of proper seal loading.Moreover, it is possible to design the clamp such that the stressesresulting from high bending loads are acceptable, while the deflectionsthat result from the high bending cause leakage of the clamp. Excessivedeflections of the clamp body induce high bending stresses in the boltsas well. High bending stresses in the bolts, since the bolts aregenerally seated on the side flanges which will deflect annularly withincreases in clamp curvature deflection.

Therefore it is generally desirable to design a clamp which meets threecriteria. That is, the clamp must meet at least the minimum acceptablecriteria for clamp wall thickness, clamp body bending stress and boltbending stress. This may be achieved in accordance with the presentinvention by adjusting the off-set distance 78 and the body wallthickness to achieve a clamp having a more desirable bending moment andhaving a decreased weight.

In general terms, the minimum criteria for clamp wall thickness may becomputed according to accepted or standard codes such as, for example,the ASME codes or their equivalent for cylindrical vessels of the samediameter and material as the clamp body. AMSE, Section 8, Division 2gives additional criteria for safe bending stress levels. Under theserules a basic stress allowable may be established for any material used.Furthermore, the allowable level of the sum of membrane (tensile) stressand bending stress is 11/2 times the basic allowable stress. It will beappreciated that the bolting material will generally have a differentlimit of allowable stress than the clamp body since different materialsare used and different methods exist for computing basic allowablelimits for bolting than for vessel materials.

Once the basic allowable stresses are established, the allowablecriteria for bending plus tensile stresses will result.

FIG. 9 displays a clamp 80 having an off-set distance 78.9 between thewall load centerline 74.9 and bolt force centerline 42.9. The clamp iscomposed of opposing clamp members 12.9 and 12.10. In that the off-setdistance 78.9 is equal to 0, then the bending load or bending moment isequal to 0 because the bending moment is equal to the product of theoff-set distance and the bolting force. Although the bending loads havebeen eliminated in clamp 80, this configuration is not the lightestpossible since the side or bolting flanges 30.9 and 30.10 must begreatly increased in order to provide the necessary space for thebolting. It is thus better to have some bending moment than no moment.As the bolting flanges 30 are moved out away from the wall centerline74, the side flanges 30 may be shortened to accommodate the clamp wall36, therefore resulting in a decreased clamp weight. However, as theoff-set distance 78 is increased, bending loads become greater and thusthe required wall thickness to resist the bending loads. Therefore, theoff-set distance 78 must be optimized to achieve a minimized clampweight.

It will be appreciated that although a fully minimized (minimum) clampweight is generally preferred, it may nevertheless be desirable, forcertain applications, to provide a clamp having a partially minimizedweight (i.e., a partially optimized off-set).

In order to determine the optimum geometry (lightest weight), dataprocessing, preferably in the form of a computer program, may beutilized to iteratively design a clamp. Such data processing isdiscussed in greater detail below.

FIG. 10 shows a typical clamp 82 made in accordance with the presentinvention. The clamp has a pair of complementary clamping members 12.11and 12.12 to be clamped together to complete the clamp, each clampingmember 12 having a clamp wall 84.11 and 84.12 defining an outer wallsurface 86 and a curved inner wall surface 38.10. The clamp wall 84.12defines a wall centerline 74.10 projected along a radial path extendingfrom a mid point between the inner surface 38.10 and outer surface 86.It will be appreciated by those of skill in the art that the mid pointreferred to is not necessarily a geometrical mid point per se, ratherthis refers to a force mid point within the clamp wall 84. However, thewall load centerline 74 will follow a radial path which generallycorresponds to the curvature of the curved inner wall surface 38.

Bolting or side flanges 30.11 and 30.12 are laterally spaced at opposedcircumferential ends of the clamp wall 84 for use in bolting theclamping members 12.11 and 12.12 to complete the pipe clamp 82. Eachbolting flange 30 has at least one bolt hole 32 for receiving a bolt 40,the bolt hole 32 defining a bolt force centerline 42, wherein thedistance between the bolt force centerline 42 and the wall centerline 84represents a centerline off-set distance 78.

It will be appreciated that by decreasing the off-set distance 78, anon-circular bore 72.10 or 72.9 will result. Such non-circular bore72.10 is generally characterized by opposing curved inner wall surfaces38.10 and 38.11 and opposed planar inner wall surfaces 88 10 and 88.11.However, such inner wall surfaces 88.10 and 88.11 are not necessarilyplanar. Therefore, such inner wall surfaces 88 may be defined moregenerally as an inner flange wall surface 88.

Therefore, it will be appreciated, that the present invention may bedefined in terms of the shape of a cross-section of the clamp body bore72, with the noncircular shape generally indicating an optimized clampbody shape. Moreover such shape may be further defined with reference tothe relative distances between opposing clamp body inner wall surfaces88.10 and 88.11 as compared to the distance between opposing curvedinner wall surfaces 38.10 and 38.11, with the curved inner wall diameterbeing generally greater than the diameter between the planar, oralternatively, the flange inner wall surfaces 88.10 and 88.11.

In a preferred embodiment the distance between opposing curved innerwall surfaces 38.10 and 38.11 is at least 1% greater than the distancebetween opposing inner flange surfaces 88.10 and 88.11. A still morepreferred embodiment may be realized by providing up to a 25% differencebetween opposing inner flange diameter and opposing curved inner walldiameter. It has been found that an optimized body shape for smallerclamps generally exhibits a greater difference between these distancesthan in larger clamps. For example, 2" clamps (that is, clamps designedfor 2" pipes) have been prepared which exhibit a 25% difference.Moreover, 16" clamps made to the same specification were found toexhibit a 10% difference whereas 48" clamps may demonstrate only a 3%.However, optimized clamps made for different applications may vary.

Pipe clamps made in accordance with the present invention may similarlybe defined by comparing the radius of the generally annular wall forcecenterline 74 to the radius (i.e., half) of the distance betweenopposing flange inner wall surfaces 88.10 and 88.11. Accordingly, thewall centerline radius may be defined as by the radius of the annularwall force centerline 74.10. Thus, the advantages of the presentinvention may be realized by maintaining the radius of the distancebetween opposing flange inner wall surfaces 88.10 and 88.11 at a valuewhich is less than the wall centerline radius.

In a preferred embodiment the flange radius is within 1% less than thewall centerline radius.

In a more preferred embodiment the flange radius is within 5% less thanthe wall centerline radius.

In still more preferred embodiment, the flange radius can be 25% lessthan the wall centerline radius.

It can be appreciated from the foregoing that an important part of thepresent invention is the clamp weight optimization which is achieved byvarying tensile load off-sets 78.

FIG. 11 illustrates a chart which demonstrates the advantages which maybe realized. Shown therein is a graphical display of changes in clampweight (along the Y) axis versus changes in off-set distances (along theX axis). It is particularly noteworthy, and particularly surprising,that a unique optimum off-set dimension exists. As illustrated, anoff-set distance of zero results in a clamp weight which is somewhatgreater than the clamp weight achievable at the optimum off-set distancevalue. The totally circular body of the conventional repair clamp (forexample see FIG. 8) gives a clamp of high weight relative to both theoptimum off-set distance and the zero off-set distance

In order to generate the optimization data as generally illustrated byFIG. 11, it is preferable to utilize data processing, preferably in theform of a computer software program.

FIG. 12 illustrates a logic circuit for minimization of clamp weight.Those of skill in the art will recognize that such logic circuit may beadaptable by those of skill in the art to perform within the frameworkof a computer software program. However, it is not absolutely necessaryto utilize computer software, as calculations for the various stresses,deflections and physical dimension may be achievable by non-softwarerelated means, such as manual calculation. However, it will be generallyrecognized that computer software has the advantage of being much lesstime consuming and potentially more accurate, in arriving at properoptimized clamp dimensions.

In a very general manner, the logic circuits of FIG. 12 iterativelydesigns a clamp. The program starts by designing for the case wherethere is no off-set (i.e., off-set equals zero). The logic circuitcomputes all of the appropriate parameters for the clamp design and thencomputes the weight. The program then increases the off-set dimension bya small increment and completes the process again. After each designiteration, the following weight is compared to the weight for thepreceding step. As long as the weight continues to decrease, the processis repeated. After a sufficient number of times, a minimum clamp weightwill be found. Such an iterative logic circuit can be used todemonstrate the finding that a unique optimum off-set dimension doesexist and that this optimum can be approached "smoothly" by the logiccircuit (i.e., no radical changes in the weight were observed with smallchanges in the off-set dimension). These conditions were successfullymet and therefore the procedure works effectively at finding anoptimized geometry for any given clamp design requirement.

In particular, the logic circuit of FIG. 12 begins at input block 90 byinputting the pipe size 92 (in terms of the pipe's outer diameter) andthe sealing length 94, which is the minimum distance between thelaterally spaced circumferential seals 18 which will accommodate, forexample, a hole in the pipeline to be repaired. Additional inputsinclude the pressure rating 96 of the clamp to be produced and thenumber of bolts 98. The number of bolts is generally based upon thedetermined bolt area requirements and by the preference of the designer.In practice, a reasonable number of bolts can be selected. Once theminimized weight has been determined, the number of bolts can be variedto alter the diameters of the individual bolts. This will alter the boltcenterline position. The minimized weight can then again be determinedand so on until the best number of bolts to give the best weight hasbeen determined. The print key is set to 0 as an internal counter.

After inputting the four above-mentioned variable inputs, the logiccircuit then proceeds to logic box 100 which computes the clearance ofthe sealing flange inner wall surfaces 14 over the pipe to be repaired.Generally, for example, a 3/16" inch clearance is typical for a 4" pipe.However, formulas which take into account potential pipe expansion andunevenness may be used to generate such clearance data, and suchformulas are well-known to those skilled in the art of clampmanufacturer. Generally, the clearance may be set at the maximumacceptable tolerance of the pipe. In a preferred embodiment, theclearance is set at twice the maximum acceptable tolerance.

The next logic step 102 involves locating the longitudinal seal alongthe seating face 34 of the clamp member 12 in line with the positioningof the ends of the circumferential seals 18.

Next, at logic circuit box 104, the pressure loading on the clamp isdetermined with reference to American Society of Mechanical Engineers(ASME) codes. In particular, gasket retention loading must be sufficientto produce enough squeeze on the seal to maintain the pressure. Thus thepressure applied over the rectangular area as defined by a cross-sectionof the clamp load bearing cavity (i.e.--the cross sectional area sealedas defined by the outer edges of the longitudinal and circumferentialseals) defines the total load and therefore determines bolt loadingwhich is also definable as the pressure loading.

At logic box 106, the cross-sectional bolt size necessary to counteractthe pressure loading is established by the allowable tensile stress forthe bolt material as determined from the pressure loading information atlogic box 104. This is a generally standard computation known to thoseof skill in the art.

Logic circuit box 108 locates the bolt centerline 42 wherein the inneredge of the bolt hole is located just outside of the longitudinal seal.

Logic circuit box 110 sets the centerline of the body shell 74 equal tothe bolt centerline 42 (therefore setting the off-set distance equal to0).

Logic circuit boxes 112-120 are concerned with computing the physicaldimensions of a clamp which meets minimum criteria for clamp wallthickness, clamp body bending stress and bolt bending stress. At box112, the shell wall thickness is computed according to standards forclamp wall thicknesses necessary to meet specified pressure loadings.For example, Section 8, Division 1 of the ASME codes specifies thegeneral rules relating to wall thickness for pressure vessels. However,other specifications may be referred to where appropriate. Accordingly,box 114 computes physical dimensions of a clamp having the selectedoff-sets and shell wall thickness. Such physical dimension computationsinclude, for example, considerations of the fact that bolt nuts 46 willnormally wedge against the outer clamp body 36 in order to obtain themaximum advantages of the present invention.

Logic circuit box 116 computes the internal stresses and deflections ofthe clamp having the physical dimensions previously determined. Thisincludes, for example, the tensile stress on the body due to pressure.The bending stress on the body is determined by dividing the moment (theproduct of the load and the off-set) in the clamp shell by the sectionmodulus of the clamp, wherein the moment is equal to the pressureloading per each clamp member 12. The section modulus of bending is aconventional calculation whereby the shell is considered a beam.

Allowable tensile stress in the body may be determined with respect toASME codes, Section 8, Division 2 which specifies more specificoperating criteria.

Whatever tensile stress allowable is determined to be appropriate withreference to the codes, the sum of the tension and bending stress isallowed to be approximately 11/2 times greater. Therefore, whateverprimary membrane allowable stress for the material is, 11/2 times thatallowable stress can be used for the sum of tension and bending stress.These are criteria for bending stress in the bolts and bending stress inthe body.

The appropriate ASME codes are the codes currently preferred fordetermining the specified criteria.

At logic box 118 the stresses and deflections calculated at box 116 arechecked against ASME standards, and if they do not the wall thickness isincrementally increased at box 120 and the computations of boxes 114-118repeated.

Once a clamp which meets the specified minimum requirements is generatedby boxes 112-120, the weight of the resultant clamp is computed at box122. Logic box 124 is a print key test which is acuated only when aclamp of minimum weight is achieved.

At logic box 126 a further test is undertaken to determine if the weightof the clamp generated at the present iteration is less than the clampachieved at the previous iteration. Basically, this test requires thatthe computations be continued until a clamp of minimum weight isachieved.

At logic box 128 the clamp weight of the present iteration is saved forcomparison with the clamp achieved at the next iteration. At logic box130 the off-set distance is incrementally increased and the nextiteration is begun.

Iterations are continued until a clamp is generated which has a greaterweight than the previous iteration (determined at box 126). When thisoccurs, the logic circuit drops back to the previous iteration whichgenerated a clamp of decreased weight and the off-set distance is againset at the previous value at logic box 130 (wherein the print key is setequal to 1). During this final iteration, the print key test at box 124is actuated and the design data printed at box 132.

Further modifications and alternative embodiments of the apparatus ofthis invention will be apparent to those skilled in the art in view ofthis disclosure. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the manner of carrying out the invention. It is to be understoodthat the forms of the invention herewith shown and described are to betaken as the presently preferred embodiments. Various changes may bemade in the shape, size and arrangement of parts. For example,equivalent elements or materials may be substituted for thoseillustrated and described herein, parts may be reversed, and certainfeatures of the invention may be utilized independently of the use ofother features, all this would be apparent to one skilled in the artafter having the benefit of this description of the invention.

What is claimed is:
 1. A clamp for forming a seal on a pipelinesection:(a) the clamp comprising at least two complementary clampmembers to be clamped together on a pipeline section to complete theclamp; (b) each clamp member having an inner surface with a pair ofaxially spaced, circumferentially extending circumferential seals; (c)at least one clamp member having at least one longitudinal seal whichextends axially to bridge the gap between a pair of circumferentialseals and define two junction zones where the two circumferential sealsand longitudinal seal abut; and (d) retention means at each junctionzone, each retention means penetrating at least one of the seals toconnect the seals together in the junction zone;wherein at least oneclamp member has a pipe branch extending therefrom.
 2. A clamp accordingto claim 1, in which each retention means is connected to a clamp memberto connect the seals with which it is engaged, to the clamp member.
 3. Aclamp according to claim 1, in which each retention means extendsthrough one of the seals and penetrates the adjacent seal to connectthem together.
 4. A clamp according to claim 3, in which each retentionmeans comprises a self tapping screw which extends through one seal andis screwed into the adjacent seal.
 5. A clamp according to claim 4, inwhich the clamp member has bores through which the screws extend tothereby secure the seals with which they are engaged, in position on theclamp member.
 6. A clamp according to claim 5, in which the seals arelocated in seal grooves in the clamp members.
 7. A clamp according toclaim 1, including at least one additional retention means which isconnected to one clamp member and penetrates one of the seals in aconnection zone to connect that seal to the clamp member in thatconnection zone.
 8. A clamp according to claim 7, including a pluralityof additional retention means which connect the seals to theirrespective clamp members in a plurality of connection zones.
 9. A clampaccording to claim 1, comprising a pair of clamp members to be clampedtogether on a pipeline section to complete the clamp, one clamp memberhaving a pair of circumferentially spaced, axially extendinglongitudinal seals positioned to bridge the gap between thecircumferential seals at the opposed ends of the circumferential sealsto define four junction zones, and four retention means which areconnected to the clamp member and connect the seals together at thejunction zones to connect the seals to the clamp member at the junctionzones.
 10. A clamp according to claim 9, which is in the form of a highpressure pipeline repair clamp and which includes additional retentionmeans which are engaged with the other clamp member and with thecircumferential seals of that clamp member by penetrating them toconnect them to the clamp member.
 11. A clamp according to claim 1, inwhich the clamp member includes clamping flanges which extend fromopposed ends of the clamp members for use in clamping the clamp memberstogether to complete the clamp.
 12. A clamp according to claim 11, inwhich each clamp flange has at least one bolt hole for receiving boltmeans for bolting the clamp members together, and including bolt meanshaving socket heads.
 13. A clamp according to claim 1, in which theclamp members have heat protection grooves in their inner surfacesbetween the peripheral axial edges of the clamp members and thecircumferential seals to protect the circumferential seals from heatflow toward the seals during welding of such peripheral axial edges. 14.A clamp according to claim 1, having corner seals positioned to abut thejunction zones and provide secondary sealing for the junction zonesduring use.
 15. A clamp according to claim 14, in which the corner sealsare located in corner recesses provided in the clamp member which hasthe junction zones.
 16. A clamp according to claim 1, in which the clampmember having the pipe branch extending therefrom has an annular gasketto seal a peripheral zone proximate the pipe branch, to a pipelinesection when the clamp is sealingly engaged with a pipeline section. 17.A clamp according to claim 1, in which one clamp member has a test port.18. A clamp for a tubular member, the clamp having an inner wallsurface, having a seal groove in the inner wall surface to house sealmeans, the seal groove being spaced from a peripheral zone of the clamp,and the clamp having a radially extending heat protection grove separatefrom the seal groove, the heat protection groove being provided in theinner wall surface and spaced between the peripheral zone of the clampand the seal groove to interrupt heat flow from the peripheral zone tothe seal groove to thereby partially protect seal means when used in theseal groove during use, against heat flow from the peripheral zoneduring welding thereof the clamp further having a pipe branch extendingtherefrom.
 19. A clamp for pipeline repair, the clamp comprising aplurality of clamp members to be clamped to each other about a pipelineto be repaired to complete the clamp, each clamp member having a sealingzone for receiving seal means and each clamp member having a radiallyextending heat protection groove that is separate from the sealing zoneand spaced between the sealing zone and a peripheral zone of the clampmember to interrupt heat flow from the peripheral zone to the sealingzone during welding of the peripheral zone and thereby provideprotection for seal means when positioned in the sealing zone, whereinat least one clamp member has a pipe branch extending therefrom.
 20. Aclamp according to claim 19, in which each clamp member has an innerwall surface, in which each sealing zone comprises a sealing groove inthe inner wall surface for housing seal means, and in which each heatprotection groove is provided in the inner wall surface.
 21. A clampaccording to claim 20, in which each clamp member is curved, in whicheach clamp member has a pair of axially spaced, circumferentiallyextending sealing grooves spaced inwardly of its axially directedperipheral edges, and in which each clamp member has a circumferentiallyextending heat protection groove between each sealing groove and itsadjacent clamp peripheral edge.
 22. A clamp according to claim 20 orclaim 21, in which the heat protection grooves have depths generallycorresponding to the depths of the sealing grooves.
 23. A clamp forforming a seal in a pipeline section:(a) at least one clamp memberhaving at least one longitudinal seal which extends axially to bridgethe gap between the ends of a pair of circumferential seals and definetwo corner junction zones; (b) at least one clamp member having at leastone corner seal positioned to abut a junction zone during use andprovide back-up sealing for the junction zone when the clamp iscompleted during use; and (c) at least one clamp member having a pipebranch extending therefrom.
 24. A clamp according to claim 23, in whichthe clamp member having the corner junction zones has a corner sealpositioned at each corner junction zone.
 25. A clamp according to claim24, in which each corner seal is positioned to embrace the outwardlydirected edges of the seals in the corner junction zones.
 26. A clampaccording to claim 24 or claim 25, in which each corner seal is locatedin a corner recess provided in the clamping member.
 27. A clampaccording to claim 26, in which each corner recess has a depth inrelation to the thickness of its cover seal, to provide for 30 to 40%compression of the corner seal when the clamp is completed.
 28. A clampaccording to claim 24, having a pair of clamp members, and having a pairof longitudinal seals to define four carrier junction zones, and havinga corner seal positioned at each corner junction zone.
 29. A clampaccording to claim 28, in which the pair of longitudinal seals areprovided on one of the clamp members, and in which all four corner sealsare provided at the corner junction zones of that clamp member to engagesealingly with the other clamp member when the clamp is completed inuse.